/**
 * Copyright (c) 2015 The JobX Project
 * <p>
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements. See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership. The ASF licenses this file
 * to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License. You may obtain a copy of the License at
 * <p>
 * http://www.apache.org/licenses/LICENSE-2.0
 * <p>
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package com.jobxhub.common.util;

public final class MurmurHash {

    public MurmurHash() {

    }

    private byte[] toBytesWithoutEncoding(String str) {

        int len = str.length();
        int pos = 0;
        byte[] buf = new byte[len << 1];
        for (int i = 0; i < len; i++) {

            char c = str.charAt(i);
            buf[pos++] = (byte) (c & 0xFF);
            buf[pos++] = (byte) (c >> 8);
        }
        return buf;
    }

    public int hashcode(String str) {
        byte[] bytes = toBytesWithoutEncoding(str);
        return hash32(bytes, bytes.length);
    }

    /**
     * * Generates 32 bit hash from byte array of the given length and  * seed.
     * *  * @param data byte array to hash  * @param length length of the array
     * to hash  * @param seed initial seed value  * @return 32 bit hash of the
     * given array
     */
    public int hash32(final byte[] data, int length, int seed) {
        // 'm' and 'r' are mixing constants generated offline.
        // They're not really 'magic', they just happen to work well.
        final int m = 0x5bd1e995;
        final int r = 24;
        // Initialize the hash to a random value
        int h = seed ^ length;
        int length4 = length / 4;
        for (int i = 0; i < length4; i++) {
            final int i4 = i * 4;
            int k = (data[i4 + 0] & 0xff) + ((data[i4 + 1] & 0xff) << 8)
                    + ((data[i4 + 2] & 0xff) << 16)
                    + ((data[i4 + 3] & 0xff) << 24);
            k *= m;
            k ^= k >>> r;
            k *= m;
            h *= m;
            h ^= k;
        }
        // Handle the last few bytes of the input array
        switch (length % 4) {
            case 3:
                h ^= (data[(length & ~3) + 2] & 0xff) << 16;
            case 2:
                h ^= (data[(length & ~3) + 1] & 0xff) << 8;
            case 1:
                h ^= (data[length & ~3] & 0xff);
                h *= m;
        }
        h ^= h >>> 13;
        h *= m;
        h ^= h >>> 15;
        return h;
    }

    /**
     * * Generates 32 bit hash from byte array with default seed value.  *  * @param
     * data byte array to hash  * @param length length of the array to hash  * @return
     * 32 bit hash of the given array
     */
    public int hash32(final byte[] data, int length) {
        return hash32(data, length, 0x9747b28c);
    }

    public int hash32(final String data) {
        byte[] bytes = toBytesWithoutEncoding(data);
        return hash32(bytes, bytes.length, 0x9747b28c);
    }

    /**
     * * Generates 64 bit hash from byte array of the given length and seed.  *
     * * @param data byte array to hash  * @param length length of the array to
     * hash  * @param seed initial seed value  * @return 64 bit hash of the
     * given array
     */
    public long hash64(final byte[] data, int length, int seed) {
        final long m = 0xc6a4a7935bd1e995L;
        final int r = 47;
        long h = (seed & 0xffffffffL) ^ (length * m);
        int length8 = length / 8;
        for (int i = 0; i < length8; i++) {
            final int i8 = i * 8;
            long k = ((long) data[i8 + 0] & 0xff)
                    + (((long) data[i8 + 1] & 0xff) << 8)
                    + (((long) data[i8 + 2] & 0xff) << 16)
                    + (((long) data[i8 + 3] & 0xff) << 24)
                    + (((long) data[i8 + 4] & 0xff) << 32)
                    + (((long) data[i8 + 5] & 0xff) << 40)
                    + (((long) data[i8 + 6] & 0xff) << 48)
                    + (((long) data[i8 + 7] & 0xff) << 56);
            k *= m;
            k ^= k >>> r;
            k *= m;
            h ^= k;
            h *= m;
        }
        switch (length % 8) {
            case 7:
                h ^= (long) (data[(length & ~7) + 6] & 0xff) << 48;
            case 6:
                h ^= (long) (data[(length & ~7) + 5] & 0xff) << 40;
            case 5:
                h ^= (long) (data[(length & ~7) + 4] & 0xff) << 32;
            case 4:
                h ^= (long) (data[(length & ~7) + 3] & 0xff) << 24;
            case 3:
                h ^= (long) (data[(length & ~7) + 2] & 0xff) << 16;
            case 2:
                h ^= (long) (data[(length & ~7) + 1] & 0xff) << 8;
            case 1:
                h ^= (long) (data[length & ~7] & 0xff);
                h *= m;
        }
        ;
        h ^= h >>> r;
        h *= m;
        h ^= h >>> r;
        return h;
    }

    /**
     * * Generates 64 bit hash from byte array with default seed value.  *  * @param
     * data byte array to hash  * @param length length of the array to hash  * @return
     * 64 bit hash of the given string
     */
    public long hash64(final byte[] data, int length) {
        return hash64(data, length, 0xe17a1465);
    }


    public long hash64(final String data) {
        byte[] bytes = toBytesWithoutEncoding(data);
        return hash64(bytes, bytes.length);
    }
}